As reported by TVGuide.com, Jess' sibling is a troublemaker, and Jess (Zooey Deschanel) will have to bail her out of a big predicament. The actress starts filming later this week, and her first appearance will air in February.

In addition to her series roles on Freaks and Geeks and ER, Cardellini is also known for her role on Mad Men this past season as Don's neighbor (and now-former mistress!) Sylvia, a role for which she earned an Emmy nomination.

New Girl airs Tuesdays at 9/8c on Fox. What do you think of the casting?